| gvSIG desktop 1

"""TELNET client class.

Based on RFC 854: TELNET Protocol Specification, by J. Postel and

J. Reynolds

Example:

>>> from telnetlib import Telnet

>>> tn = Telnet('www.python.org', 79)   # connect to finger port

>>> tn.write('guido\r\n')

>>> print tn.read_all()

Login       Name               TTY         Idle    When    Where

guido    Guido van Rossum      pts/2        <Dec  2 11:10> snag.cnri.reston..

>>>

Note that read_all() won't read until eof -- it just reads some data

-- but it guarantees to read at least one byte unless EOF is hit.

It is possible to pass a Telnet object to select.select() in order to

wait until more data is available.  Note that in this case,

read_eager() may return '' even if there was data on the socket,

because the protocol negotiation may have eaten the data.  This is why

EOFError is needed in some cases to distinguish between "no data" and

"connection closed" (since the socket also appears ready for reading

when it is closed).

Bugs:

- may hang when connection is slow in the middle of an IAC sequence

To do:

- option negotiation

- timeout should be intrinsic to the connection object instead of an

  option on one of the read calls only

"""

# Imported modules

import sys

import socket

import select

__all__ = ["Telnet"]

# Tunable parameters

DEBUGLEVEL = 0

# Telnet protocol defaults

TELNET_PORT = 23

# Telnet protocol characters (don't change)

IAC  = chr(255) # "Interpret As Command"

DONT = chr(254)

DO   = chr(253)

WONT = chr(252)

WILL = chr(251)

theNULL = chr(0)

class Telnet:

    """Telnet interface class.

    An instance of this class represents a connection to a telnet

    server.  The instance is initially not connected; the open()

    method must be used to establish a connection.  Alternatively, the

    host name and optional port number can be passed to the

    constructor, too.

    Don't try to reopen an already connected instance.

    This class has many read_*() methods.  Note that some of them

    raise EOFError when the end of the connection is read, because

    they can return an empty string for other reasons.  See the

    individual doc strings.

    read_until(expected, [timeout])

        Read until the expected string has been seen, or a timeout is

        hit (default is no timeout); may block.

    read_all()

        Read all data until EOF; may block.

    read_some()

        Read at least one byte or EOF; may block.

    read_very_eager()

        Read all data available already queued or on the socket,

        without blocking.

    read_eager()

        Read either data already queued or some data available on the

        socket, without blocking.

    read_lazy()

        Read all data in the raw queue (processing it first), without

        doing any socket I/O.

    read_very_lazy()

        Reads all data in the cooked queue, without doing any socket

        I/O.

    """

    def __init__(self, host=None, port=0):

        """Constructor.

        When called without arguments, create an unconnected instance.

        With a hostname argument, it connects the instance; a port

        number is optional.

        """

        self.debuglevel = DEBUGLEVEL

        self.host = host

        self.port = port

        self.sock = None

        self.rawq = ''

        self.irawq = 0

        self.cookedq = ''

        self.eof = 0

        if host:

            self.open(host, port)

    def open(self, host, port=0):

        """Connect to a host.

        The optional second argument is the port number, which

        defaults to the standard telnet port (23).

        Don't try to reopen an already connected instance.

        """

        self.eof = 0

        if not port:

            port = TELNET_PORT

        self.host = host

        self.port = port

        self.sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

        self.sock.connect((self.host, self.port))

    def __del__(self):

        """Destructor -- close the connection."""

        self.close()

    def msg(self, msg, *args):

        """Print a debug message, when the debug level is > 0.

        If extra arguments are present, they are substituted in the

        message using the standard string formatting operator.

        """

        if self.debuglevel > 0:

            print 'Telnet(%s,%d):' % (self.host, self.port),

            if args:

                print msg % args

            else:

                print msg

    def set_debuglevel(self, debuglevel):

        """Set the debug level.

        The higher it is, the more debug output you get (on sys.stdout).

        """

        self.debuglevel = debuglevel

    def close(self):

        """Close the connection."""

        if self.sock:

            self.sock.close()

        self.sock = 0

        self.eof = 1

    def get_socket(self):

        """Return the socket object used internally."""

        return self.sock

    def fileno(self):

        """Return the fileno() of the socket object used internally."""

        return self.sock.fileno()

    def write(self, buffer):

        """Write a string to the socket, doubling any IAC characters.

        Can block if the connection is blocked.  May raise

        socket.error if the connection is closed.

        """

        if IAC in buffer:

            buffer = buffer.replace(IAC, IAC+IAC)

        self.msg("send %s", `buffer`)

        self.sock.send(buffer)

    def read_until(self, match, timeout=None):

        """Read until a given string is encountered or until timeout.

        When no match is found, return whatever is available instead,

        possibly the empty string.  Raise EOFError if the connection

        is closed and no cooked data is available.

        """

        n = len(match)

        self.process_rawq()

        i = self.cookedq.find(match)

        if i >= 0:

            i = i+n

            buf = self.cookedq[:i]

            self.cookedq = self.cookedq[i:]

            return buf

        s_reply = ([self], [], [])

        s_args = s_reply

        if timeout is not None:

            s_args = s_args + (timeout,)

        while not self.eof and apply(select.select, s_args) == s_reply:

            i = max(0, len(self.cookedq)-n)

            self.fill_rawq()

            self.process_rawq()

            i = self.cookedq.find(match, i)

            if i >= 0:

                i = i+n

                buf = self.cookedq[:i]

                self.cookedq = self.cookedq[i:]

                return buf

        return self.read_very_lazy()

    def read_all(self):

        """Read all data until EOF; block until connection closed."""

        self.process_rawq()

        while not self.eof:

            self.fill_rawq()

            self.process_rawq()

        buf = self.cookedq

        self.cookedq = ''

        return buf

    def read_some(self):

        """Read at least one byte of cooked data unless EOF is hit.

        Return '' if EOF is hit.  Block if no data is immediately

        available.

        """

        self.process_rawq()

        while not self.cookedq and not self.eof:

            self.fill_rawq()

            self.process_rawq()

        buf = self.cookedq

        self.cookedq = ''

        return buf

    def read_very_eager(self):

        """Read everything that's possible without blocking in I/O (eager).

        Raise EOFError if connection closed and no cooked data

        available.  Return '' if no cooked data available otherwise.

        Don't block unless in the midst of an IAC sequence.

        """

        self.process_rawq()

        while not self.eof and self.sock_avail():

            self.fill_rawq()

            self.process_rawq()

        return self.read_very_lazy()

    def read_eager(self):

        """Read readily available data.

        Raise EOFError if connection closed and no cooked data

        available.  Return '' if no cooked data available otherwise.

        Don't block unless in the midst of an IAC sequence.

        """

        self.process_rawq()

        while not self.cookedq and not self.eof and self.sock_avail():

            self.fill_rawq()

            self.process_rawq()

        return self.read_very_lazy()

    def read_lazy(self):

        """Process and return data that's already in the queues (lazy).

        Raise EOFError if connection closed and no data available.

        Return '' if no cooked data available otherwise.  Don't block

        unless in the midst of an IAC sequence.

        """

        self.process_rawq()

        return self.read_very_lazy()

    def read_very_lazy(self):

        """Return any data available in the cooked queue (very lazy).

        Raise EOFError if connection closed and no data available.

        Return '' if no cooked data available otherwise.  Don't block.

        """

        buf = self.cookedq

        self.cookedq = ''

        if not buf and self.eof and not self.rawq:

            raise EOFError, 'telnet connection closed'

        return buf

    def process_rawq(self):

        """Transfer from raw queue to cooked queue.

        Set self.eof when connection is closed.  Don't block unless in

        the midst of an IAC sequence.

        """

        buf = ''

        try:

            while self.rawq:

                c = self.rawq_getchar()

                if c == theNULL:

                    continue

                if c == "\021":

                    continue

                if c != IAC:

                    buf = buf + c

                    continue

                c = self.rawq_getchar()

                if c == IAC:

                    buf = buf + c

                elif c in (DO, DONT):

                    opt = self.rawq_getchar()

                    self.msg('IAC %s %d', c == DO and 'DO' or 'DONT', ord(c))

                    self.sock.send(IAC + WONT + opt)

                elif c in (WILL, WONT):

                    opt = self.rawq_getchar()

                    self.msg('IAC %s %d',

                             c == WILL and 'WILL' or 'WONT', ord(c))

                    self.sock.send(IAC + DONT + opt)

                else:

                    self.msg('IAC %s not recognized' % `c`)

        except EOFError: # raised by self.rawq_getchar()

            pass

        self.cookedq = self.cookedq + buf

    def rawq_getchar(self):

        """Get next char from raw queue.

        Block if no data is immediately available.  Raise EOFError

        when connection is closed.

        """

        if not self.rawq:

            self.fill_rawq()

            if self.eof:

                raise EOFError

        c = self.rawq[self.irawq]

        self.irawq = self.irawq + 1

        if self.irawq >= len(self.rawq):

            self.rawq = ''

            self.irawq = 0

        return c

    def fill_rawq(self):

        """Fill raw queue from exactly one recv() system call.

        Block if no data is immediately available.  Set self.eof when

        connection is closed.

        """

        if self.irawq >= len(self.rawq):

            self.rawq = ''

            self.irawq = 0

        # The buffer size should be fairly small so as to avoid quadratic

        # behavior in process_rawq() above

        buf = self.sock.recv(50)

        self.msg("recv %s", `buf`)

        self.eof = (not buf)

        self.rawq = self.rawq + buf

    def sock_avail(self):

        """Test whether data is available on the socket."""

        return select.select([self], [], [], 0) == ([self], [], [])

    def interact(self):

        """Interaction function, emulates a very dumb telnet client."""

        if sys.platform == "win32":

            self.mt_interact()

            return

        while 1:

            rfd, wfd, xfd = select.select([self, sys.stdin], [], [])

            if self in rfd:

                try:

                    text = self.read_eager()

                except EOFError:

                    print '*** Connection closed by remote host ***'

                    break

                if text:

                    sys.stdout.write(text)

                    sys.stdout.flush()

            if sys.stdin in rfd:

                line = sys.stdin.readline()

                if not line:

                    break

                self.write(line)

    def mt_interact(self):

        """Multithreaded version of interact()."""

        import thread

        thread.start_new_thread(self.listener, ())

        while 1:

            line = sys.stdin.readline()

            if not line:

                break

            self.write(line)

    def listener(self):

        """Helper for mt_interact() -- this executes in the other thread."""

        while 1:

            try:

                data = self.read_eager()

            except EOFError:

                print '*** Connection closed by remote host ***'

                return

            if data:

                sys.stdout.write(data)

            else:

                sys.stdout.flush()

    def expect(self, list, timeout=None):

        """Read until one from a list of a regular expressions matches.

        The first argument is a list of regular expressions, either

        compiled (re.RegexObject instances) or uncompiled (strings).

        The optional second argument is a timeout, in seconds; default

        is no timeout.

        Return a tuple of three items: the index in the list of the

        first regular expression that matches; the match object

        returned; and the text read up till and including the match.

        If EOF is read and no text was read, raise EOFError.

        Otherwise, when nothing matches, return (-1, None, text) where

        text is the text received so far (may be the empty string if a

        timeout happened).

        If a regular expression ends with a greedy match (e.g. '.*')

        or if more than one expression can match the same input, the

        results are undeterministic, and may depend on the I/O timing.

        """

        re = None

        list = list[:]

        indices = range(len(list))

        for i in indices:

            if not hasattr(list[i], "search"):

                if not re: import re

                list[i] = re.compile(list[i])

        while 1:

            self.process_rawq()

            for i in indices:

                m = list[i].search(self.cookedq)

                if m:

                    e = m.end()

                    text = self.cookedq[:e]

                    self.cookedq = self.cookedq[e:]

                    return (i, m, text)

            if self.eof:

                break

            if timeout is not None:

                r, w, x = select.select([self.fileno()], [], [], timeout)

                if not r:

                    break

            self.fill_rawq()

        text = self.read_very_lazy()

        if not text and self.eof:

            raise EOFError

        return (-1, None, text)

def test():

    """Test program for telnetlib.

    Usage: python telnetlib.py [-d] ... [host [port]]

    Default host is localhost; default port is 23.

    """

    debuglevel = 0

    while sys.argv[1:] and sys.argv[1] == '-d':

        debuglevel = debuglevel+1

        del sys.argv[1]

    host = 'localhost'

    if sys.argv[1:]:

        host = sys.argv[1]

    port = 0

    if sys.argv[2:]:

        portstr = sys.argv[2]

        try:

            port = int(portstr)

        except ValueError:

            port = socket.getservbyname(portstr, 'tcp')

    tn = Telnet()

    tn.set_debuglevel(debuglevel)

    tn.open(host, port)

    tn.interact()

    tn.close()

if __name__ == '__main__':

    test()